Chuang Han

Enhancing the visible light photocatalytic performance of ternary CdS–(graphene–Pd) nanocomposites via a facile interfacial mediator and co-catalyst strategy

By embedding noble metal palladium (Pd) into the interfacial layer matrix of graphene (GR) and semiconductor CdS, we have successfully constructed ternary CdS–(GR–Pd) nanocomposites with intimate interfacial contact. The CdS–(GR–Pd) nanocomposites show remarkably enhanced photocatalytic activity toward selective redox reactions under visible light irradiation as compared to blank-CdS and the optimum binary CdS–GR. It is revealed that the photocatalytic performance enhancement of CdS–(GR–Pd) is ascribed to the optimized spatial charge carrier transfer across the interface resulting from the introduction of Pd nanoparticles as mediators into the interfacial layer between GR and CdS. One role of Pd is to serve as electron reservoir to directly trap photogenerated electrons from CdS and the other role is as interfacial mediator to promote electron relay in the ternary CdS–(GR–Pd) photocatalysts along with conductive graphene as dual co-catalysts. Moreover, the negative light “shielding effect” of GR can be partially counterbalanced through such a facile strategy. This work substantiates the feasibility of adopting the “interfacial-mediator” strategy to optimize the interfacial charge carriers transfer pathway and efficiency for improved photoactivity of GR–semiconductor nanocomposites toward target photoredox reactions.

Photocatalytic water splitting for solar hydrogen generation: fundamentals and recent advancements

The expected depletion of fossil fuel reserves and its serious environmental impact have emphasised the issue of sustainable development of the human society. Solar hydrogen by photocatalytic water splitting is a promising alternative to conventional fossil fuels, which is of great potential to relieve the energy and environmental issues and bring an energy revolution in a clean and sustainable manner. This review is going to make a brief introduction of the basic principles of photocatalytic water splitting and the concept of different kinds of water splitting systems. Various engineering strategies for searching higher efficiency of water splitting based on the photocatalytic processes, including light harvesting, charge carriers separation and co-catalysts loading, have been outlined and discussed with selected typical examples on some elaborately designed semiconductor-based photocatalytic systems. Moreover, recent impressive progresses and advancements for photocatalytic water splitting with some promising materials are presented. Finally, this review is concluded with a summary and perspective in this hot area of research.

Heterostructured semiconductor nanowire arrays for artificial photosynthesis

The current rapid industrial development generates a high need for alternative sustainable sources of energy. Artificial photosynthesis, which can directly convert solar energy into usable or storable energy resources, provides such a promising alternative. Semiconductor nanowires have gained growing interest in artificial photosynthesis due to their unique geometrical and electronic characteristics, which can provide large aspect-ratios, direct pathways for charge transport, decoupling the direction of charge carrier collection, and low reflectance induced by light scattering and trapping. In particular, heterostructured semiconductor nanowire arrays (NWAs) have recently been of great interest in artificial photosynthesis because of their unique structural and physicochemical properties. Nanowire structure can lower the electrochemical over-potential while the heterojunctions can enhance light absorption and charge separation, which thus increase the artificial photosynthesis efficiency of heterostructured semiconductor NWAs. In this review, we will highlight recent advances in the application of heterostructured semiconductor NWAs to artificial photosynthesis. An emphasis will be placed on the unique characteristics and benefits of using heterostructured semiconductor NWAs with different heterojunctions for artificial photosynthesis, as well as the associated challenges and directions for future research in this area.

One dimensional CdS based materials for artificial photoredox reactions

Semiconductor-based heterogeneous photocatalysis has received considerable attention as an alternative promising approach to alleviate the globally increasing energy demand and environmental concerns. As promising candidates, one dimensional (1D) CdS nanostructures have gained growing interest due to their unique advantages, including a narrow band gap, suitable band edge positions, high aspect ratio structure with low reflectance, and excellent electronic charge transfer. This review summarizes a panorama of the latest progress related to the design and construction of 1D CdS based photocatalysts with boosted performance, involving constructing 1D solid solution, loading cocatalysts, coupling with semiconductors, hybridizing with carbon-based materials and functionalization with biocatalysts. Finally, some challenges and opportunities for future exploration of 1D CdS based photocatalysts are critically discussed. It is anticipated that this review will afford enriched information on the rational utilization of 1D CdS materials with ameliorated performances by harnessing their inherent merits, and particularly stimulate further developments of low dimensional heterostructures towards various artificial photoredox reactions.

Progressive Design of Plasmonic Metal–Semiconductor Ensemble toward Regulated Charge Flow and Improved Vis–NIR-Driven Solar-to-Chemical Conversion

Surface plasmon resonance (SPR)-mediated photocatalysis without the bandgap limitations of traditional semiconductor has aroused significant attention in solar-to-chemical energy conversion. However, the photocatalytic efficiency barely initiated by the SPR effects is still challenged by the low concentration and ineffective extraction of energetic hot electrons, slow charge migration rates, random charge diffusion directions, and the lack of highly active sites for redox reactions. Here, the tunable, progressive harvesting of visible-to-near infrared light (vis-NIR, λ > 570 nm) by designing plasmonic Au nanorods and metal (Au, Ag, or Pt) nanoparticle codecorated 1D CdS nanowire (1D CdS NW) ensemble is reported. The intimate integration of these metal nanostructures with 1D CdS NWs promotes the extraction and manipulated directional separation and migration of hot charge carriers in a more effective manner. Such cooperative synergy with tunable control of interfacial interaction, morphology optimization, and cocatalyst strategy results in the distinctly boosted performance for vis-NIR-driven plasmonic photocatalysis. This work highlights the significance of rationally progressive design of plasmonic metal-semiconductor-based composite system for boosting the regulated directional flow of hot charge carrier and thus the more efficient use of broad-spectrum solar energy conversion.